As an apparatus assisting the driving of a vehicle such as an automobile, a vehicle-mounted camera obtaining an image of a range including the dead area from a driver's viewing field and a vehicle-mounted monitor displaying an image obtained by the vehicle-mounted camera are used. For example, a camera is attached to the rear face of the vehicle. Then, an image obtained by image obtaining of the field behind the vehicle is displayed on a vehicle-mounted monitor. This allows the driver to drive the vehicle into the garage with checking the field behind the vehicle on the basis of the image displayed on the vehicle-mounted monitor. Further, a camera is attached to the front face of the vehicle. Then, an image obtained by image obtaining of the field in the left and right front of the vehicle is displayed on a vehicle-mounted monitor. This allows the driver to check the presence of children, obstacles, and the like around the vehicle at a crossing or the like on the basis of the image displayed on the vehicle-mounted monitor.
In such a driving assistance apparatus, a plurality of cameras are mounted on the vehicle. Then, the image from each camera is switched and displayed. Alternatively, the images from the plurality of cameras are composited and displayed. This expands the field checked by the driver on the basis of the image displayed on the vehicle-mounted monitor. According to Japanese Laid-open Patent Publication No. 2007-36668, an apparatus has been proposed in which images from cameras attached in the front, rear, left, and right of a vehicle are composited so that the entire surroundings of the vehicle is displayed on a vehicle-mounted monitor. Such an apparatus allows the driver to check at once the entire situation around the vehicle on the basis of the image displayed on the vehicle-mounted monitor. This reduces an influence to driver's driving operation caused by the driver's operation of checking the vehicle-mounted monitor.
As described above, when images obtained by a plurality of cameras are to be composited, the cameras are arranged such that their viewing fields partly overlap with each other. Then, in the overlapping fields obtained by a plurality of cameras, the images obtained by the cameras are composited. Here, a seam of images arises in the compositing position where the plurality of images are composited. In the field near such a seam, discontinuity in the image may be caused by a difference in the viewpoint of each camera. This discontinuity may generate a situation that an intrinsically present obstacle is not detected on the image data.
In order to resolve such a problem, an apparatus has been proposed in which the compositing position used at the time of compositing a plurality of images is variable. Nevertheless, in such an apparatus, only a few kinds of compositing position patterns are prepared. Then, in many cases, the compositing position pattern is switched when a given condition is satisfied. Thus, when the compositing position of the image is switched, the display image is changed. This causes in some cases a rapid change in the manner that the object in the display image is seen and there is a possibility that the driver gets confused.